Every telemetry will at least transmit users' IP address (by the nature of how requests are made), which is legally considered private information.

Even if that was not the case, a privacy respecting (any?) browser has no business sending any information from my machine, including "I crashed because of OoM" unless I explicitly allow it to do so.

Zero telemetry by default is the only acceptable standard for any browser that claims to be privacy respecting (which Firefox does).